1. Field of the Invention
Centrifugal surface finishing apparatus; improved sealing means between a relatively-rotating bottom and an outer upstanding wall of the finishing chamber thereof; method and means for providing and maintaining such seal employing a hydrostatic head or pressure of liquid, e.g., water or finishing compound solution, in a manner which prevents fouling of said seal by "fines" produced by attrition of finishing material and/or workpieces during the finishing process.
2. Prior Art
Apparatus and methods for the surface finishing of parts or workpieces by attrition with finishing material or media comprising relatively large finishing particles, also known as finishing chips, in a finishing chamber in the presence of a liquid vehicle, is well-established in the prior art. One type of finishing is known as centrifugal finishing and involves the employment of an apparatus having a containing surface comprising a bottom and an upstanding wall which are symmetrically arranged about a common axis and which are relatively rotatable about said axis in order to impart motion to the contents of the finishing chamber. In such apparatus, the bottom of the finishing chamber generally rotates relative to an outer upstanding wall, which is usually stationary, and through centrifugal action causes the contents to move radially outward toward and to impinge upon such upstanding wall.
Representative apparatus and method and seals for the juncture of the finishing chamber bottom member and the outer upstanding wall member are to be found in U.S. Pat. Nos. 4,177,608; 3,435,565; 3,990,188; and 4,026,075, as well as in German Offenlegungsschrift 2,705,445. In the apparatus of these patents, a seal is usually provided which prevents outflow of liquid vehicle or "compound" from the finishing chamber and such seals generally involve a rubbing contact between flat or irregular surfaces of the seal and the bottom, of the seal and the upstanding wall, or of the seal itself. Such seals are essential whether the type of apparatus is solely centrifugal in nature or whether resilient mounting means, such as springs or elastomer, are employed at some point beneath the finishing chamber and/or a vibratory action is imposed upon the centrifugal action, or employed as a part of the finishing process such as in an emptying phase. The presence of such a seal is required in all known centrifugal embodiments due to the relative motion between the finishing chamber bottom and the outer upstanding wall thereof.
All such arrangements to date have been costly, inefficient, have required excessive power for overcoming the considerable friction between the relatively-moving surfaces, and conducive to excessive wear, necessitating frequent replacement of the sealing means, and have moreover not been effective in eliminating the fouling of the seal between the relatively-rotating bottom of the finishing chamber and the outer upstanding wall thereof by the "fines" produced during the finishing process by attrition of the finishing material and/or the parts or workpieces being finished. This is true even though lubrication of the seal has sometimes been effected by the employment of a pump and associated equipment to force lubricating fluid into the seal. Due to deficiencies in the structure of the apparatus and of the seals previously available and in the method employed for finishing, including effecting and maintaining such seal, and especially for drainage of fluid from the finishing chamber which, at least partially, has generally involved return or drainage of fluid and entrained fines through the seal or to the same source from which the liquid vehicle was originally pumped, previous equipment and procedure leaves much to be desired. Thus, all prior art approaches to date, whether of the "closed system" or of the "flow through" type, and all known variations thereof, have imposed serious limitations upon the employment of such centrifugal apparatus and method. The present invention provides a superior and highly advantageous structure and seal and fulfils a long-felt need for the same, while concurrently avoiding the shortcomings of the prior art and thereby providing unprecedented efficiency, durability, and economy in this type of apparatus and method, and especially premitting complete control of tolerances in the seal, use of much closer tolerances in the seal, and the maintenance of such tolerances during long periods of operation, said seal moreover being effectively self purging.